Vacuum circuit interrupter having improved contact structure

ABSTRACT

A vacuum type circuit interrupter is provided having a contact structure comprising separable mating contacts. The contact structure is constructed so that the mating contacts close on a first material and open on a second material. The first material on which the mating contacts close is made from weld free material so that contact welding does not occur when the vacuum interrupter is closed. The second material on which the contacts open, possesses good contact opening characteristics and interrupting that is, opening of the contacts will occur without excess current chopping.

United States Patent [191 Harrold Dec. 11, 1973 VACUUM CIRCUITINTERRUPTER HAVING IMPROVED CONTACT STRUCTURE Inventor: Ronald T.Harrold, Murrysville, Pa.

Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed: June 23, 1972 Appl. No.: 265,904

Assignee:

US. Cl 200/144 B, 200/146 R Int. Cl. H011! 33/66 Field of Search 200/144B, 146 R,

References Cited UNITED STATES PATENTS 7/1943 Thumim 200/146 R 7/1959Reece 200/144 B X 3,017,480 1/1962 Klaassen 200/146 R PrimaryExaminerRobert S. Macon Attorney-A. T. Stratton et al.

[ ABSTRACT 9 Claims, 9 Drawing Figures I /l I g q I 4 l v I I 32 \\/IBVACUUM CIRCUIT INTERRUITER HAVING IMPROVED CONTACT STRUCTURE BACKGROUNDOF THE INVENTION The present invention relates to vacuum type circuitinterrupters and more particularly to the contact structure which is apart of such vacuum interrupters. The contact structures disclosedutilize the principle of closing on a first material which has goodclosing characteristics, and resists welding, and opening on a secondmaterial which interrupts the circuit without current chopping forimproved vacuum interrupter operation. Vacuum type circuit interruptersgenerally comprise an evacuated insulatingenvelope with separablecontacts disposed within the insulating envelope. The contacts aremovable between a closed position in which the contacts are engaged andan open position where the contacts are separated and an arcing gap isestablished therebetween. An arc is initiated between the contactsurfaces when the contacts move into or out of engagement while thecircuit in which the interrupter is used is energized.

When the contacts are brought together the are that is formed -meltssome of the metallic contact material. After the contacts are broughttogether under high pressure engagement welds may be formed betweenrequired to break the weld so that the contacts can-beopened, dependsupon many factors including the arc voltage, the current, the contactarea and the contact material. These welds are objectionable since theyinterfere with the easy movement of the separable contacts and mayresult in the failure of the vacuum interrupter to open.

Another difficulty that is encountered with some prior art contacts invacuum interrupters is that the materials used have an excessivetendency to chop under low current conditions. Thissharp chop in'current can induce extremely high voltages acrossinductive devicesconnected in the circuit beinginterrupted, and such overvoltages canlead'to destruction of the circuit components. For an effective vacuuminterrupter, there should not be an excessive current chop on circuitopening.

Copper tungsten is ideal for weld free closing but poor on openings dueto current chopping and also has undersirable electron emission. Chromedue to its vapor pressure properties is goodfor weld free closing,however, it has disadvantages of high contact resistance and isexpensive. in the required oxygen-free form. One of thebest materialsfor opening is copper, but this welds easily on contact closing. Thussome materials are best for closing, others best for opening and acompromise is made by using metal mixtures or alloys. Contacts made fromcopper bismuth or chrome copper construction have reasonably goodopening and closing characteristics, however, they still require anexpensive contact release mechanism. It-is felt that the presentinvention has significant advantages over prior art contacts in that thecontacts close on a-material that is weld free and open on a materialthat has good nonchopping characteristics.

SUMMARY OF THE INVENTION This invention discloses contact constructionswhich effectively use closing on a first material which has goodnon-welding characteristics and opening on a second material which doesnot cause excessive current chopping, and which has good interruptingcharacteristics. This improves operation of the vacuum interrupter. Anexpensive release mechanism is not required to assist in weld breakingand also the interrupter in its final closed position how low contactresistance.

In one embodiment of the invention, the contacts are brought together ona material which has good nonweld characteristics and then the contactsare moved to a final closed position where contact is made through amaterial having low resistance and good nonchopping characteristics. Thecontact points are moved from the first material to the second materialby moving the operating rod transverse to the longitudinal axis of thevacuum interrupter. On vacuum interrupter opening, the contacts separateon the second material which has good non-chopping properties.

In another embodiment of the invention, the stationary contact isdisposed within the vacuum interrupter. A movable contact is attached toan operating rod which moves along the longitudinal axis of the vacuuminterrupter. The movable contact is pivotally attached to the operatingrod so that when the vacuum interrupter is closed first contact is madeon a material which has good non-weld characteristics and as theoperating rod closes further the movable contact pivots around theoperating rod and contact is made with a second material which has goodopening characteristics. When the vacuum interrupter is opened, themovable contact is returned to and held in position for another closingoperation by ceramic magnets which are attached to the movable contactand the operating rod. Current is carried from the movable contact totheoperating rod by a flexible connection.

In another embodiment of the invention two identical semicircularcontacts each made of two materials are disposed within the vacuuminterrupter. One of the contacts is pivotally attached to a stationaryconducting rod. The other contact is pivotally attached to the movableoperating rod. The movable operating rod moves along the longitudinalaxis of the vacuum interrupter to move the contacts into and out ofengagement. The arrangement is such that when the two contacts are inthe open position, they are held in position by coil springs. Whenbrought together, under' pressure, they make contact on a first materialthen revolve around the respective pivots continuously making electricalcontact until a final closed position is reached in which contact ismade on a second material. The contacts close on a weld free materialand under increasing pressure the contacts roll over each other to thefinal closed position. Surge current flows initially through'this weldfree material while the contacts roll over each other, until, by thetime normal current is flowing contact is made on a second materialwhich has good conductivity and desirable opening characteristics. Onopening, the arc is formed between this second material and minimumcurrent chopping is experienced. This embodiment of the invention canprevent welding of contacts even if the contacts are made of a materialhaving poor weld characteristics, such as copper, by virtue of thecontact rolling motion on closing which prevents welding. The currentwhich flows when contact motion has ceased being insufficient forcontact welding.

In anotherembodiment of the invention, two sets of contacts are used inthe vacuum interrupter, one for closing and one for opening. The firstset of contacts are located in the center of the second set of contactsso that the second set of contacts form an annular contact ringsurrounding the first set of contacts. In this way, a weld free materialcan be used for the closing contacts and a material without currentchopping properties can be used for the opening contacts. An expensiverelease mechanism is not required, and also the interrupter in its finalclosed position has low contact resistance. In a closing operation, thecontact structure first closes on the centrally located contacts whichare made of a weld free material. The surrounding second set of contactsof high conductivity material with good opening characteristics thenclose. After a slight time delay, the first set of contacts open and thevacuum interrupter is in the fully closed position. On opening, thesecond set of contacts interrupt the current flow without chopping.

Devices utilizing the teaching of the present invention have severaladvantages over the prior art. For example, there is no contact weldingon vacuum interrupter closing. Another advantage of the presentinvention is that there is minimal current chopping on contact openingand the contacts separate on a material having good current interruptingcharacteristics. Another advantage is that there is reduced contact wearsince the contacts close on a non-welding noneroding material. Anotheradvantage of the present invention is that when the vacuum interrupteris in the fully closed position, the contacts are closed on a materialwhich has low contact resistance. Still another advantage of the presentinvention is that an expensive mechanism to release welded contacts isnot required.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages of the presentinvention will be readily apparent upon reading the followingdescription taken in conjunction with the drawings, in which:

FIG. 1 is a vertical sectional view of a vacuum type circuit interrupterwith the contacts in the open position embodying a contact constructionof the present invention;

FIG. 2 is a side view partially in section of the vacuum interruptershown in FIG. 1 with the contacts in the fully closed position;

FIG. 3 is a side view partially in section of another embodiment of theinvention with the contacts in the open position;

FIG. 4 is similar to FIG. 3 but with the contacts in the closedposition;

FIG. 5 is a side view of a pair of contacts illustrating anotherembodiment of the invention;

FIG. 6 is a view of the contacts shown in FIG. 5 with the contacts inthe closed position; I

FIG. 7 is a vertical sectional view of still another embodiment of theinvention with the contacts in the open position;

FIG. 8 is a view of a portion of the vacuum interrupter shown in FIG. 7with the contacts in an intermediate closed position; and

FIG; 9 is a side view partially in section of the vacuum interruptershown in FIG. 7 with the contacts in the fully closed position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingsand more particularly to FIGS. 1 and 2, there is shown a vacuum typecircuit interrupter l0 embodying the teaching of the present invention.The vacuum type circuit interrupter 10 comprises a highly evacuatedenvelope 12 formed of glass or suitable ceramic material and a pair ofmetallic end caps 14 and 16 and the insulating envelope 12 to render theenvelope l2 vacuum tight. The vacuum in the envelope 12 under normaloperating conditions is lower than 10 Torr so that mean free path ofelectrons will be longer than the potential breakdown distance withinthe tubular envelope l2.

Disposed within the envelope 12 are a pair of relatively movableelectrodes or contacts 20 and 22 embodying the teaching of the presentinvention. As shown in FIG. 1, when these contacts 20 and 22 areseparated there is an arcing gap 24 formed therebetween. The uppercontact 20 is stationary and is secured to a conducting rod 26 by asuitable means such as welding or brazing. The conducting rod 26 issecured at its upper end to the stationary end cap 14 by suitable meanssuch as welding or brazing. The lower contact 22 is movable and isjoined to a conducting operating rod 28. The conducting operating rod 28is suitably mounted for movement along the longitudinal axis of thetubular insulating envelope 12 and for a slight motion transverse to thelongitudinal axis of the tubular insulating envelope 12. The movableoperating rod 28 projects through an opening 30 in the bellows end cap16.

As shown in FIGS. 1 and 2, a flexible metal bellows 32 is secured insealing relationship at its respective opposite ends to movableoperating rod 28 and the opening 30 in the bellows end cap 16. Theflexible metal bellows 32 provides a seal about the rod 28 to allow formovement of the rod 28 without impairing the vacuum inside theinsulating envelope l2.

Coupled to the lower end of the operating rod 28 suitable actuatingmeans (not shown) is provided for driving the movable contact 22 upwardinto engagement with the stationary contact 20 so as to close theinterrupter 10. The actuating means is also capable of returning thecontacts 22 to its open position so as to open the interrupter 10. Thecircuit opening operation will for example entail a typical gap lengthwhen the contacts are fully separated of approximately one-half inch.

When contacts 20 and 22 ofa vacuum interrupter 10 are opened, at thebeginning of circuit interruption, a metallic arc initiates between theseparated contacts 20 and 22 and serves as a vehicle for currentconduction until the arc is extinguished. In an alternating currentcircuit the arc is usually extinguished near the first current zero ofthe alternating current wave. The are that is established across thearcing gap 24 between the contacts 20 and 22 when they are opened, andalso when they are closed, vaporizes and melts some of the contactmaterial. The vapors are dispersed from the arcing gap 24 toward theinside of the insulating envelope 12.-The internal surfaces of theinsulating envelope 12 are protected from the condensation of the arcgenerated metallic vapor and particles thereon by means of a tubularmetallic shield 36. The tubular metallic shield 36 is supported on theinsulating envelope l2 and preferably electrically isolated from bothend caps 14 and 16. This shield 36 acts to intercept and condense arcgenerated .metallic vapors before they can reach the internal surfacesof the insulating envelope 12. To reduce the possibility that metallicvapors or particles can bypass the main shield 36 and coat the internalsurface of the insulating envelope 12 a pair of end shields 38 and 40are provided at opposite ends of the central shield 36.

The contacts 20 and 22 comprise two portions, a first portion of anon-welding material 52 such as chrome, copper tungsten, or the like,and the second portion 54 comprises a material having low resistance andnonchopping properties such as copper or the like. When the contacts 20and 22 are closed, initial engagement occurs on the non-welding material52. After initial engagement of the contacts 20 and 22 the operatingmeans (not shown) moves operating rod 28 transverse to the longitudinalaxis of the interrupter so that the contact points shift fromnon-welding material 52 to the low resistance non-chopping material 54.As shown in FIG. 2, in the final closed position, contact is made on thesecond material 54 which has good opening characteristics. Duringopening of the interrupter 10, final contact parting occurs on thesecond material 54.

In another embodiment of the invention shown in FIGS. 3 and 4, themovable contact 22 is pivotally attached to the operating rod 28. Theoperating rod 28 is supported for movement along the longitudinal axisof the interrupter 10. The contacts are comprises of a first material 52having non-welding characteristics and a second material 54 having lowresistance, nonchopping characteristics. As shown in FIG. 3, when thevacuum interrupter is in the open position, the movable contact 22 isheld in position by a magnet 56 attached to contact 22 and a magnet 58attached to the movable operating rod 28. The movable contact 22 isattached to the operating rod 28 through a ceramic bearing 60. Currentflows from the movable contact 22 to the operating rod 28 through aflexible connection 62. During the closing operation of the vacuuminterrupter 10 initial contact between the contacts 20 and 22 is made onthe non-welding material 52. As the operating rod 28 continues to movetoward the closed position, along the longitudinal axis of theinterrupter 10, the movable contact 22 moves about the pivot 60 so thatfinal contact is made on a second material 54, as shown in FIG. 4.During circuit opening, final contact parting takes place on the secondmaterial 54 which has good opening characteristics. The operating rod 28moves the contact 22 to the fully open position very rapidly so that thecircuit is interrupted before the movable contact 22 returns to theposition as shown in FIG. 3.

Referring now to FIGS. 5 and 6 there are shown a pair of vacuuminterrupter contacts illustrating another embodiment of the presentinvention. The first contact 64 is pivotally attached to the stationaryconducting rod 26. A second contact 66 is pivotally attached to themovable operating rod 28. Each contact 64 and 66 is made from a firstmaterial 52 having good non-welding characteristics and a secondmaterial 54 having good circuit opening characteristics. The contactarrangement is such that when the contacts 64 and 66 are broughttogether under pressure, engagement is first made between the firstmaterial 52 which is weld free and then the two contacts revolve aroundtheir respective pivots 68 and continuously making a good electricalcontact until when the contacts are fully closed, contact is madebetween the second material 54 having good opening characteristics.Opening of the contacts will occur between the materials 54 having goodopening characteristics with minimum current chopping.

Contacts 64 and 66 are identical and semicircular in construction. Thecontacts 64 and 66 pivot on ceramic bearings 68 and 70, respectively.The contacts 64 and 66 are held in the open position by flat spiralsprings 72 and 74, respectively, when the contacts are disengaged, asshown in FIG. 5. When the contacts 64 and 66 are brought together underpressure, they revolve around the respective pivot bearings 68 and 70continuously making electrical contact until in the final closedposition, as shown in FIG. 6, contact is made between the secondmaterial 54 having good opening characteristics. On circuit interruptionthe movable operating rod 28 moves rapidly to the open position, beforethe flat spiral springs 72 and 74 can rotate the contacts 64 and 66, sothat opening occurs on the second material 54. A flexible connection 76electrically connects contact 64 to conducting rod 26. A flexibleconnection 78 connects contacts 66 with the movable operating rod 28.Thus when the contacts are in the closed position as shown in FIG. 6 acontinuous current path extends from the conducting rod 26, through theflexible connection 76, through the second material 54 of contact 64,through the second material 54 of contact 66, through the flexibleconnection 78, to the movable operating rod 28. This design is such thaton closing any metallic vapor formed due to arcing between the closingcontacts 64 and 66, will be directed away from the final closingsurfaces. Likewise, during an opening operation, any metallic vaporexpelled from the contacts will be directed away from the point whereinitial contact engagement is made.

The embodiment of the invention illustrated in FIGS. 5 and 6 willprevent contact welding even if the contacts 64 and 66 are made of onematerial such as copper, since the contact rolling motion on closingprevents welding. When contact motion has ceased the current thenflowing is insufficient for welding of the contacts 64 and 66. Manyvariations and improvements are possible with this construction ofcontact. For example, by suitably grading the resistivity of the contactarea used for closing and opening, and by controlling the motions ofcontacts 64 and 66 the are initially formed between the low contactsresistance material 54 would experience an increasing resistive path asit continued between the high resistance material while finallyextinguished as the contacts separate further. This would be a type ofresistive opening.

Referring now to FIGS. 7, 8 and 9, there is shown a movable contactstructure 80 and a stationary contact structure 82 disposed within avacuum interrupter 10. In this embodiment of this invention, two sets ofcontacts are used in a vacuum interrupter. One set made out of anon-welding material 52 for closing, and the other set made out ofmaterial with non-chopping characteristics 54 for opening. The lowercontact structure 82 which is relatively stationary comprises a centralcontact made of non-welding material 52, an outer contact 92 made of anon-chopping material 54, an outer housing 94, a compression spring 96to resilv iently support contacts 90 and 92, and flexible connections 98to electrically connect the contacts 90 and 92 to end'cap 14. The outercontact 92 is joined to the central contact 90 by suitable means such aswelding or brazing. Conducting studs 100 are mounted on the end cap 14for making electrical contact and for mounting the vacuum interrupter10. Movable contact structure 80 comprises, a central contact 81 made ofa nonwelding material 52, an annular surrounding contact 83 made of anon-chopping material 54, a compression spring 84 for moving contact 81relative to contact 83, and an operating means (not shown) for movingcontact structure 80 into and out of engagement with contact structure82. A cup-shaped shield 85 surrounds the flexible metallic bellows 32 toprevent the bellows 32 from being bombarded by particles expelled duringcontact arcing. A metal bellows 33 is attached to reset rod 86 to permitmovement of the reset rod 86 to return contact 81 to its normal openposition upon opening of vacuum interrupter 10.

Referring now to FIG. 7, vacuum interrupter is shown in its normal openposition. The first step in the closing operation of vacuum interrupter10 is shown by dashed lines 87 in FIG. 7. As the vacuum interrupter 10is closed, the contact structure 80 moves toward the contact structure82 and the central contacts 81 and 90 engage as shown by the dashedlines 87 in FIG. 7. As the contact structure 80 continues to close, theouter contacts 83 of contact structure 80 begins to move relative to thestationary contact 81. In the open position contact 81 is heldstationary with respect to contact 83 by spring loaded ball bearings 102engaging a circular depression 104 in supporting rod 106. As the contactstructure 80 continues to move toward the closed position after contacts81 and 90 touch, the rod 106 is disengaged from the position shown inFIG. 7 where it is held stationary by the spring loaded bearings 102,and moves toward the position shown in FIG. 9 where it is heldstationary by the spring loaded bearings 108 engaging the circulardepression 104. As the rod 106 is disengaged from the spring loadedbearings 102, and starts to move relative to the outer portion 88 ofcontact structure 80 the outer portion 88 is moving faster than the rod106 tends to be moved by spring 84, so that before contacts 81 and 90separate contacts 83 and 92 engage, as shown in FIG. 8. As shown in FIG.8, contacts 81 and 90 remain engaged until after contacts 83 and 92 areengaged. After contacts 83 and 92 are engaged, and fully closed so thatcontact 83 is no longer moving, rod 106 continues to move from theposition where it was held stationary by bearings 102 to the position asshown in FIG. 9 where it is held stationary by the spring loadedbearings 102, and moves toward the position shown in FIG. 9 where it isheld stationary by the spring loaded bearings 108 engaging the circulardepression 104. As the rod 106 is disengaged from the spring loadedbearings 102, and starts to move relative to the outer portion 88 ofcontact structure 80 the outer portion 88 is moving faster than the rod106 tends to be moved by spring 84, so that before contacts 81 and 90separate contacts 83 and 92 engage, as shown in FIG. 8. As shown in FIG.8, contacts 81 and 90 remain engaged until after contacts 83 and 92 areengaged. After contacts 83 and 92 are engaged, and fully closed so thatcontact 83 is no longer moving, rod 106 continues to move from theposition where it was held stationary by bearings 102 to the position asshown in FIG. 9 where it is held stationary by spring loaded bearings108. As the rod 106 continues to move towards position where bearings108 engage the depression 104, the centrally located contacts 81 and 90separate so that the final closed position is as shown in FIG. 9. Thevacuum interrupter 10 is now closed on contacts 83 and 92 which are madefrom a material 54 having good opening characteristics. When the vacuuminterrupter 10 opens contacts 83 and 92 separate with little currentchopping. As contact structure moves towards the open position a resetmeans (not shown) operates the reset rod 86 to move the rod 106 from theposition where it is held stationary by spring loaded bearings 108 tothe position where it is held stationary by spring loaded bearings 102.The interrupter 10 is then in fully opened position as shown in FIG. 7and ready for another closing operation.

This invention has advantages over prior art contacts in that there isno contact welding on closing and there is little current chopping onopening. Another advantage is that there is reduced contact wear becauseof closing on a non-welding material. Other advantages are that when thecontacts are in the fully closed position, they are closed on contactmaterial having low contact resistance, also no expensive releasemechanism to break welded contact is required.

Since numerous changes may be made in the above described apparatus, anddifferent embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all the mattercontained in the foregoing description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

l. A vacuumtype circuit interrupter comprising a highly evacuatedinsulating envelope, a first contact structure disposed within saidinsulating envelope, a second contact structure disposed within saidinsulating envelope, said second contact structure being movable betweena first position in contact with said first contact structure and asecond position in which said second contact structure is spaced fromsaid first contact structure to establish an arcing gap therebetween,said first contact structure comprising a first portion constructed froma material having good nonwelding characteristics and a second portionconstructed from a material having low resistivity and good openingcharacteristics, said second contact structure comprising a firstportion having good non-weld characteristics and a second portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure, when said vacuum type circuit interrupter is fully closedsaid second portion of said second contact is in engagement with saidsecond portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact.

2. A vacuum type circuit interrupter comprising a highly evacuatedinsulating envelope, a first contact structure disposed within saidinsulating envelope, a second contact structure disposed within saidinsulating envelope, said second contact structure being movable betweena first position in contact with said first contact structure and asecond position in which said second contact structure is spaced fromsaid first contact structure to establish an arcing gap therebetween,said first contact structure comprising a first portion constructed froma material having good nonwelding characteristics and a second portionconstructed from a material having low resistivity and good openingcharacteristics, said second contact structure comprising a firstportion having good non-weld characteristics and asecond portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure, when said vacuum type circuit interrupter is fully closedsaid second portion of said second contact is in engagement with saidsecond portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact, andincluding a stationary conducting means to which said first contact isrigidly attached, operating means to which said second contact isrigidly attached, said operating means being supported for movementalong a longitudinal axis defined by said conducting means and formovement transverse to the longitudinal axis defined by said conductingmeans, and in which when said vacuum interrupter is closed said firstportion of said second contact initially engages said first portion ofsaid first contact and then said second portion of said second contactengages said second portion of said first contact and said first portionof said first contact is disengaged from said first portion of saidsecond contact.

3. A vacuum type circuit interrupter as claimed in claim 2, wherein saidfirst portion of said first contact and said second portion of saidfirst contact are rigidly joined, and said first portion of said secondcontact and said second portion of said second contact are rigidlyjoined.

4. A vacuum type circuit interrupter comprising a highly evacuatedinsulating envelope, a first contact structure disposed within saidinsulating envelope, a second contact structure disposed within saidinsulating envelope, said second contact structure being movable betweena first position in contact with said first contact structure and asecond position in which said second contact structure is spaced fromsaid first contact structure to establish an arcing gap therebetween,said first contact structure comprising a first portion constructed froma material having good nonwelding characteristics and a second portionconstructed from a material having low resistivity and good openingcharacteristics, said second contact structure comprising a firstportion having good non-weld characteristics and a second portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure when said vacuum type circuit interrupter is fully closed saidsecond portion of said second contact is in engagement with said secondportion of said first contact and said first portion of said secondcontact and said first portion of said first contact are disengaged,when said vacuum type circuit interrupter is operated from a closedposition to an open position separation of said first contact from saidsecond contact occurs between said second portion of said first contactand said second portion of said second contact, said first portion ofsaid first contact and said second portion of said first contact arerigidly joined, and said first portion of said second contact and saidsecond portion of said second contact are rigidly joined, and aconducting rod rigidly supports said first contact structure, a movableoperating rod, said movable operating rod being supported for movementalong its longitudinal axis, said second contact structure beingpivotally supported by said movable operating rod.

5. A vacuum interrupter as claimed in claim 4 including a first magneticmeans attached to said second contact structure, a second magnetic meansattached to said movable operating rod, said first magnetic means andsaid second magnetic means cooperating to retain said second contactstructure in predetermined position when said vacuum type circuitinterrupter is open.

6. A vacuum type circuit interrupter comprising a highly evacuatedinsulating envelope, a first contact structure disposed within saidinsulating envelope, a second contact structure disposed within saidinsulating envelope, said second contact structure being movable betweena first position in contact with said first contact structure and asecond position in which said second contact structure is spaced fromsaid first contact structure to establish an arcing gap therebetween,said first contact structure comprising a first portion constructed froma material having good nonwelding characteristics and a second portionconstructed from a material having low resistivity and good openingcharacteristics, said second contact structure comprising a firstportion having good non-weld characteristics and a second portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure, when said vacuum type circuit interrupter is fully closedsaid second portion of said second contact is in engagement with saidsecond portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact, said firstportion of said first contact and said second portion of said firstcontact are rigidly joined, and said first portion of said secondcontact and said second portion of said second contact are rigidlyjoined, and including a stationary conducting rod said first contactbeing pivotally attached to said stationary conducting rod, a movableoperating rod, said second contact being pivotally attached to saidmovable operating rod, said first contact and said second contact beingsemicircular in configuration so that when said second contact movesinto engagement with said first contact a rolling contact point ismaintained and said first and said second contact structures revolvearound their respective pivot points.

7. The combination as claimed in claim 6 wherein a first spiral springis provided around the pivot point of said first contact to maintainsaid first contact in a predetermined position when said vacuuminterrupter is opened, and a second flat spiral spring provided aroundthe pivot point of said second contact structure to maintain said secondcontact structure in a predetermined position when said vacuuminterrupter is opened.

8. A vacuum type circuit interrupter comprising a highly evacuatedinsulating envelope, a first contact structure disposed within saidinsulating envelope, a second contact structure disposed within saidinsulating envelope, said second contact structure being movable betweena first position in contact with said first contact structure and asecond position in which said second contact structure is spaced fromsaid first contact structure to establish an arcing gap therebetween,said first contact structure comprising a first I portion constructedfrom a material having good nonacteristics and a second portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure, when said vacuum type circuit interrupter is fully closedsaid second portion of said second contact is in engagement with saidsecond portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact, said firstportion of said first contact structure and said second portion of saidfirst contact structure are rigidly joined, and said first portion ofsaid second contact structure is movable with respect to said secondportion of said second contact structure, and said second contactstructure comprises a first portion which is centrally located and asecond portion which forms an annular contact area around said firstportion, said first portion being supported so that when the vacuuminterrupter is closed, said first portion moves with respect to saidsecond portion.

9. The vacuum interrupter as claimed in claim 8 wherein said firstportion of said second contact structure is movable between a first andsecond position with respect to said second portion of said secondcontact structure and a spring loaded ball bearing means are provided tohold said first portion of said second contact structure in said firstand said second positions.

1. A vacuum type circuit interrupter comprising a highly evacuatedinsulating envelope, a first contact structure disposed within saidinsulating envelope, a second contact structure disposed within saidinsulating envelope, said second contact structure being movable betweena first position in contact with said first contact structure and asecond position in which said second contact structure is spaced fromsaid first contact structure to establish an arcing gap therebetween,said first contact structure comprising a first portion constructed froma material having good non-welding characteristics and a second portionconstructed from a material having low resistivity and good openingcharacteristics, said second contact structure comprising a firstportion having good non-weld characteristics and a second portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure, when said vacuum type circuit interrupter is fulLy closedsaid second portion of said second contact is in engagement with saidsecond portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact.
 2. Avacuum type circuit interrupter comprising a highly evacuated insulatingenvelope, a first contact structure disposed within said insulatingenvelope, a second contact structure disposed within said insulatingenvelope, said second contact structure being movable between a firstposition in contact with said first contact structure and a secondposition in which said second contact structure is spaced from saidfirst contact structure to establish an arcing gap therebetween, saidfirst contact structure comprising a first portion constructed from amaterial having good non-welding characteristics and a second portionconstructed from a material having low resistivity and good openingcharacteristics, said second contact structure comprising a firstportion having good non-weld characteristics and a second portion havinglow resistivity and good opening characteristics, said first contactstructure and said second contact structure being constructed so thatwhen said second contact structure moves into engagement with said firstcontact structure said first portion of said second contact structuremakes initial engagement with said first portion of said first contactstructure, when said vacuum type circuit interrupter is fully closedsaid second portion of said second contact is in engagement with saidsecond portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact, andincluding a stationary conducting means to which said first contact isrigidly attached, operating means to which said second contact isrigidly attached, said operating means being supported for movementalong a longitudinal axis defined by said conducting means and formovement transverse to the longitudinal axis defined by said conductingmeans, and in which when said vacuum interrupter is closed said firstportion of said second contact initially engages said first portion ofsaid first contact and then said second portion of said second contactengages said second portion of said first contact and said first portionof said first contact is disengaged from said first portion of saidsecond contact.
 3. A vacuum type circuit interrupter as claimed in claim2, wherein said first portion of said first contact and said secondportion of said first contact are rigidly joined, and said first portionof said second contact and said second portion of said second contactare rigidly joined.
 4. A vacuum type circuit interrupter comprising ahighly evacuated insulating envelope, a first contact structure disposedwithin said insulating envelope, a second contact structure disposedwithin said insulating envelope, said second contact structure beingmovable between a first position in contact with said first contactstructure and a second position in which said second contact structureis spaced from said first contact structure to establish an arcing gaptherebetween, said first contact structure comprising a first portionconstructed from a material having good non-welding characteristics anda second portion constructed from a material having low resistivity andgood opening characteristics, said second contact structure comprising afirst portion having good non-weld characteristics and a second portionhaVing low resistivity and good opening characteristics, said firstcontact structure and said second contact structure being constructed sothat when said second contact structure moves into engagement with saidfirst contact structure said first portion of said second contactstructure makes initial engagement with said first portion of said firstcontact structure when said vacuum type circuit interrupter is fullyclosed said second portion of said second contact is in engagement withsaid second portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact, said firstportion of said first contact and said second portion of said firstcontact are rigidly joined, and said first portion of said secondcontact and said second portion of said second contact are rigidlyjoined, and a conducting rod rigidly supports said first contactstructure, a movable operating rod, said movable operating rod beingsupported for movement along its longitudinal axis, said second contactstructure being pivotally supported by said movable operating rod.
 5. Avacuum interrupter as claimed in claim 4 including a first magneticmeans attached to said second contact structure, a second magnetic meansattached to said movable operating rod, said first magnetic means andsaid second magnetic means cooperating to retain said second contactstructure in predetermined position when said vacuum type circuitinterrupter is open.
 6. A vacuum type circuit interrupter comprising ahighly evacuated insulating envelope, a first contact structure disposedwithin said insulating envelope, a second contact structure disposedwithin said insulating envelope, said second contact structure beingmovable between a first position in contact with said first contactstructure and a second position in which said second contact structureis spaced from said first contact structure to establish an arcing gaptherebetween, said first contact structure comprising a first portionconstructed from a material having good non-welding characteristics anda second portion constructed from a material having low resistivity andgood opening characteristics, said second contact structure comprising afirst portion having good non-weld characteristics and a second portionhaving low resistivity and good opening characteristics, said firstcontact structure and said second contact structure being constructed sothat when said second contact structure moves into engagement with saidfirst contact structure said first portion of said second contactstructure makes initial engagement with said first portion of said firstcontact structure, when said vacuum type circuit interrupter is fullyclosed said second portion of said second contact is in engagement withsaid second portion of said first contact and said first portion of saidsecond contact and said first portion of said first contact aredisengaged, when said vacuum type circuit interrupter is operated from aclosed position to an open position separation of said first contactfrom said second contact occurs between said second portion of saidfirst contact and said second portion of said second contact, said firstportion of said first contact and said second portion of said firstcontact are rigidly joined, and said first portion of said secondcontact and said second portion of said second contact are rigidlyjoined, and including a stationary conducting rod said first contactbeing pivotally attached to said stationary conducting rod, a movableoperating rod, said second contact being pivotally attached to saidmovable operating rod, said first contact and said second contact beingsemicircular in configuration so that when said second contact movesinto enGagement with said first contact a rolling contact point ismaintained and said first and said second contact structures revolvearound their respective pivot points.
 7. The combination as claimed inclaim 6 wherein a first spiral spring is provided around the pivot pointof said first contact to maintain said first contact in a predeterminedposition when said vacuum interrupter is opened, and a second flatspiral spring provided around the pivot point of said second contactstructure to maintain said second contact structure in a predeterminedposition when said vacuum interrupter is opened.
 8. A vacuum typecircuit interrupter comprising a highly evacuated insulating envelope, afirst contact structure disposed within said insulating envelope, asecond contact structure disposed within said insulating envelope, saidsecond contact structure being movable between a first position incontact with said first contact structure and a second position in whichsaid second contact structure is spaced from said first contactstructure to establish an arcing gap therebetween, said first contactstructure comprising a first portion constructed from a material havinggood non-welding characteristics and a second portion constructed from amaterial having low resistivity and good opening characteristics, saidsecond contact structure comprising a first portion having good non-weldcharacteristics and a second portion having low resistivity and goodopening characteristics, said first contact structure and said secondcontact structure being constructed so that when said second contactstructure moves into engagement with said first contact structure saidfirst portion of said second contact structure makes initial engagementwith said first portion of said first contact structure, when saidvacuum type circuit interrupter is fully closed said second portion ofsaid second contact is in engagement with said second portion of saidfirst contact and said first portion of said second contact and saidfirst portion of said first contact are disengaged, when said vacuumtype circuit interrupter is operated from a closed position to an openposition separation of said first contact from said second contactoccurs between said second portion of said first contact and said secondportion of said second contact, said first portion of said first contactstructure and said second portion of said first contact structure arerigidly joined, and said first portion of said second contact structureis movable with respect to said second portion of said second contactstructure, and said second contact structure comprises a first portionwhich is centrally located and a second portion which forms an annularcontact area around said first portion, said first portion beingsupported so that when the vacuum interrupter is closed, said firstportion moves with respect to said second portion.
 9. The vacuuminterrupter as claimed in claim 8 wherein said first portion of saidsecond contact structure is movable between a first and second positionwith respect to said second portion of said second contact structure anda spring loaded ball bearing means are provided to hold said firstportion of said second contact structure in said first and said secondpositions.